# 5.10
current_users = ['Liuyi','chener','Zhangsan','lisi','Wangwu',]
new_users = ['Zhaoliu','zhangsan','zhaoba','Wujiu','zhengshi',]

current_users_lower = [user.lower() for user in current_users]
# 替代：
# current_users_lower = []
# for user in current_users:
#   current_users_lower.append(user.lower())

for new_user in new_users:
    if new_user.lower() in current_users_lower:
        print(f"{new_user}, that name is taken.")
    else:
        print(f"{new_user} is still available.")
